The process of developing software, including requirements gathering, solution design and analysis, implementation, testing, deployment, support and maintenance.
Software development (also known as application development, software design, designing software, software application development, enterprise application development, or platform development) is the development of a software product. The term "software development" may be used to refer to the activity of computer programming, which is the process of writing and maintaining the source code, but in a broader sense of the term it includes all that is involved between the conception of the desired software through to the final manifestation of the software, ideally in a planned and structured process. Therefore, software development may include research, new development, prototyping, modification, reuse, re-engineering, maintenance, or any other activities that result in software products.
Questions having the development tag regard the development of custom code in the SharePoint environment.
Reference: Wikipedia - Software development